A conventional commercial aircraft generally includes a fuselage, a pair of wings, and a propulsion system that provides thrust. The propulsion system typically includes at least two aircraft engines, such as turbofan jet engines. Each turbofan jet engine is mounted to a respective one of the wings of the aircraft, such as in a suspended position beneath the wing, separated from the wing and fuselage. Such a configuration allows for the turbofan jet engines to interact with separate, freestream airflows that are not impacted by the wings and/or fuselage. This configuration can reduce an amount of turbulence within the air entering an inlet of each respective turbofan jet engine, which has a positive effect on a net propulsive thrust of the aircraft.
However, a drag on the aircraft including the turbofan jet engines also affects the net propulsive thrust of the aircraft. A total amount of drag on the aircraft, including skin friction and form drag, is generally proportional to a difference between a freestream velocity of air approaching the aircraft and an average velocity of a wake downstream from the aircraft that is produced due to the drag on the aircraft.
Positioning a fan at an aft end of the fuselage of the aircraft may assist with reenergizing a boundary layer airflow over the aft end of the fuselage and improving propulsive efficiency. However, given existing structures at the aft end of the fuselage, such as one or more stabilizers, the airflow ingested by such a fan may not have a uniform velocity or total pressure profile along the circumferential and radial directions of the fan. More specifically, the structures at the aft end of the fuselage may generate a boundary layer or wake resulting in swirl distortion and a distorted velocity or total pressure profile of the airflow ingested by the fan.
Accordingly, an aircraft capable of energizing slow-moving air forming a boundary layer across the fuselage of the aircraft would be useful. Specifically, a fuselage of an aircraft designed to increase the ingestion of relatively low momentum boundary layer airflow into the aft engine and reduce the non-uniformity and distortion of the velocity profile of ingested airflow would be particularly beneficial.